During the period of the past fifty years, the type of glass container forming machine known in the trade as the individual section or "IS" machine, has developed increased utility such that today it is the dominant machine employed throughout the world in the manufacture of glass containers of the type employed in the packaging industry. The original IS machine is shown and described in U.S. Pat. No. 1,911,119 and produces containers by what has been popularly described as the "blow and blow process." In this basic process, a gob of glass is loaded into an inverted parison mold having neck rings at its bottom end. A baffle is applied to the open top end of the parison mold and a so called settle blowing pressure is applied to the gob of glass to force the molten glass into the cavity defined by the neck rings. Subsequently a counter blow pressure is applied through the bore of the neck rings to blow the gob of glass into intimate engagement with the walls of the parison mold and form a parison having a hollow interior. The baffle is then removed, the parison mold opened, and the inverted parison is transferred to an upright position by the neck rings where it is enclosed within the blow mold by closing two blow mold halves thereon.
The original IS machine was first expanded to increase its productivity by employing double cavity molds, then triple cavity and even quadruple cavity. The number of cavities is, of course, limited by the size of the desired article. Obviously, large containers in excess of two liters in capacity could not be blown on a standard IS machine in more than a double cavity mold. The smaller the container, the more cavities can be employed to simultaneously form such containers. It is quite common today to form twelve ounce beer bottles by triple cavity molds.
At the same time the number of cavities were increasing, the number of sections of the IS machine were substantially increased. It's not uncommon for ten sections to be operated in a common frame.
The world wide utilization of the IS machine was further promoted by the development of alternate processes which could be employed on the machine without a substantial modification thereof. One such process modification is the well known "press and blow" method of operation wherein the parison is formed in the parison mold by a pressing operation. There are now two well known versions of a press and blow mode of operation. One mode is commonly known as the "62 process" wherein the parison molds are split and the pressing is accomplished by raising a plunger through the central bore of the neck rings to compress a gob of glass that had previously been deposited within a cavity defined between the plunger and a surrounding sleeve on which the neck ring and the closable parison mold halves were supported. Such process is described in U.S. Pat. No. 2,289,046 to Rowe. A modified press and blow process, commonly known as the "41 process" is described in U.S. Pat. No. 3,024,571 to Abbott et al. In this process, the parison mold is solid and opened at both its top and bottom ends. A gob of glass is dropped through the open top end of the parison mold to rest upon a plunger inserted through the neck rings, and a baffle is then closed across the open top of the parison mold and the plunger elevated to effect the pressing of the deposited gob into conformity with the walls of the parison mold and the neck rings disposed at the bottom thereof. The baffle is then raised and swung out of position, as is the one piece parison mold, and the press molded parison is transferred by the inverting motion of the neck rings to the blow molding position.
A further modification of the blow and blow process is the utilization of vacuum to assist the initial flow of the gob of glass into the cavities of the neck rings. Following the application of such vacuum, the parison is blown into conformity with the parison mold by a counter blow pressure applied in conventional fashion. This method is commonly known as a "vacuum settle blow" method of operation or "51 process" and is described in U.S. Pat. No. 4,191,548 to Fortner et al.
On the blow mold side of the machine, process revisions have also been effected. One is the employment of vacuum applied through the interior surfaces of the blow molds to assist in the expansion of the parison into engagement with the molding surfaces.
Another process variation is the application of "puff blowing" after the opening of the baffle and prior to removal of the parison molds from the formed parison. An additional puff of air is introduced into the parison at this time and, in certain types of containers does provide improved quality in the finished product. Puff blowing is described in U.S. Pat. No. 2,273,777 to Berthold.
The most significant recent improvement in IS machines is the application of computer control to the multitude of air valving operations that must be carried out in order to cause the machine to operate in accordance with any one of the many aforedescribed process variations. As is well known, the entire operation of an IS machine depends on air, supplied at various pressures, as an actuating fluid, cooling wind and in some cases as a vacuum.
The control of the valving of each section of the original IS machine was effected through the medium of a large rotary drum having a plurality of radially adjustably positioned bolt heads projecting from the periphery of the drum and engaging valve actuators at a selected position as the drum was rotated. As additional sections were added to the machine, additional control bolts were required, hence the common configuration of the IS machine was that of a massive bottom housing within which the rotating control drums occupied the majority of the space, with a multitude of control valves disposed within and on the housing adjacent to the path of the rotary drum and connected by a maze of piping to the large number of operating cylinders and flow valves employed on each section of the machine. It necessarily followed that whenever it was desired to change the forming process being practiced by a particular machine, it was not only necessary to add additional components to the forming mechanism such as pressing plungers, when changing from blow and blow to a "press blow" operation, but, additionally, a plethora of additional pipes, valves and timing bolts had to be added to the machine to effect the conversion of the machine operation from one process to the other. In most cases, the limitations of space to accommodate such piping and valves necessarily dictated that the valves and piping employed for the previous process had to be removed, thus making the conversion from one process to another a time consuming and expensive proposal.
With the application of computer control to the IS machine, for example as described in U.S. Pat. No. 4,152,134 to Dowling et al., it became possible to employ solenoid type control valves and to locate the great majority of such solenoid control valves in one or two valve blocks which could then be disposed in a convenient location along the front faces of the top and bottom housings of the machine. The removal of the massive timing drum from the base housing of the machine provided more than adequate space for the location of the multiude of fluid conduits required to connect the solenoid control valves to the various operating cylinders of the various sections of the machine. The problem still remains, however, that whenever it is desired to shift the machine from one type of process operation to another, a substantial modification of the plumbing and wiring, and addition of solenoid valves properly connected to such plumbing and wiring had to be effected, and hence the time to convert the IS machine from one process mode to another still remains very substantial.